Obstacle Avoidance for Kinematically Redundant Manipulators in Dynamically Varying Environments

TLDR

Most obstacle‑avoidance research for manipulators focuses on pick‑and‑place tasks, but redundant degrees of freedom enable trajectory‑based avoidance suitable for spray painting and arc welding. The study aims to compute joint‑rate commands that satisfy a primary end‑effector trajectory while simultaneously enforcing obstacle‑avoidance constraints. The method decomposes the joint‑rate solution into a particular component for the trajectory and a homogeneous component that prioritizes obstacle avoidance, thereby maximizing clearance while maintaining end‑effector accuracy. An efficient numerical implementation achieves cycle times fast enough to handle dynamically changing environments.

Abstract

The vast majority of work to date concerned with obstacle avoidance for manipulators has dealt with task descriptions in the form ofpick-and-place movements. The added flexibil ity in motion control for manipulators possessing redundant degrees offreedom permits the consideration of obstacle avoidance in the context of a specified end-effector trajectory as the task description. Such a task definition is a more accurate model for such tasks as spray painting or arc weld ing. The approach presented here is to determine the re quired joint angle rates for the manipulator under the con straints of multiple goals, the primary goal described by the specified end-effector trajectory and secondary goals describ ing the obstacle avoidance criteria. The decomposition of the solution into a particular and a homogeneous component effectively illustrates the priority of the multiple goals that is exact end-effector control with redundant degrees of freedom maximizing the distance to obstacles. An efficient numerical implementation of the technique permits sufficiently fast cycle times to deal with dynamic environments.